In Thomazic, A. . . . Kamdem, Y.: “Fabrication of Bimaterial Components by Conventional Powder Metallurgy”, PM2010 World Congress—Tools for Improving PM II-Design Test & Evaluation; Bouvard, Didier (Grenoble INP/CNRS) “Fabrication of Bimaterial Components by Conventional Powder Metallurgy”, Vol.5, p.25, the powder-metallurgical production of bimaterials, i.e. components, which are constructed of two different materials, is thoroughly described. Accordingly, it is possible to fill powder of two different materials into a cavity one after the other and then jointly process these into a manageable body (green compact). In the described case, a hard and solid component of iron-based WC-hard metal (WC-Fe) is used as first material and a tough iron-based material (Fe) as second material. Compaction at 600 MPa in the case of WC-Fe material for example results in a green density of 69% TD and in the case of the Fe-rich material in 74% TD (TD: theoretical density of the material). After the joint uniaxial pressing at 600 MPa, a moulded body is created which after the sintering permits a solid composite of both materials. In order to evaluate the suitability of the press-ready granulates used and in order to understand the formation of the composite of the two materials, density curves were measured. The selected powder compositions were selected on the one hand so that the initial material densities differ only slightly and these increase to an approximately same density end value during the sintering.
It can be observed that the curves of the density change significantly differ in the range of medium temperatures. Of necessity, this must lead to mechanical stresses in the region of the bond of both materials.
Furthermore it is described that it is relevant which of the two materials was filled into the cavity first during the creation of a layer-pressed body, which indicates material interactions among the materials and with the die.
However, the evaluation of the density distribution following the pressing and the cracks observed in the component after the sintering show that the powder-technological production of valve seat rings from two materials can be technically mastered only with difficulty. Nevertheless, there are numerous applications in which such material combinations would offer technical advantages.